Literaturdatenbank
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Packard, M. J., & Packard, G. C. (1991). Sources of calcium, magnesium, and phosphorus for embryonic softshell turtles (trionyx spiniferus). Journal of Experimental Zoology, 110, 99–112.
Added by: Sarina Wunderlich (13 Oct 2008 21:33:03 UTC) Last edited by: Beate Pfau (02 Aug 2009 16:25:37 UTC) |
| Resource type: Journal Article BibTeX citation key: Packard1991c View all bibliographic details  |
Categories: General Keywords: Apalone, Apalone spinifera, Schildkröten = turtles + tortoises, Trionychidae, Zeitigung = incubation Creators: Packard, Packard Collection: Journal of Experimental Zoology |
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| Abstract |
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Eggs of softshell turtles (Trionyx spiniferus) were incubated on wet (water potential = -150 kPa) and dry (water potential = -1,500 kPa) substrates at 29°C. The rigid, heavily calcified eggshells restricted exchanges of water between eggs and their environment, but eggs exposed to wet substrates nonetheless contained more water at the end of incubation than eggs in the drier environment. However, differences in the amount of water contained by eggs had no demonstrable effect on patterns of metabolism and growth by embryos. The embryos in both treatments obtained about 75% of their calcium from the eggshell, but acquired all of their magnesium and phosphorus from the yolk. Residual yolk removed from hatchlings contained minimal quantities of all three elements. Thus, all the calcium mobilized during development was deposited in the carcass, and yolk was depleted of almost its entire store of this element. This pattern of mobilization and deposition of calcium is similar to that observed in embryos of other chelonians and in those of oviparous lepidosaurinas. In contrast, embryonic crocodilians and birds store some of the calcium mobilized from the eggshell in the yolk, and residual yolk consequently contains a substantial reserve of calcium. Our results indicate that the pattern of mobilization and deposition of calcium documented for birds and crocodilians probably is an attribute of the archosaurian lineage and not a simple result of embryos developing in rigid, heavily calcified eggshells.
Added by: Sarina Wunderlich Last edited by: Beate Pfau |